Britain may want to join the euro in five years’ time, Tony Blair said yesterday as he warned that the country would be poorer and weaker outside the European Union.

The former Prime Minister accepted that Britain could operate in the global economy if it severed ties with the EU, but he warned that such a decision would amount to a “monumental error of statesmanship” that would deprive Britain of global power and influence.

And he voiced fears that flirting with leaving the EU, as some ministers have done publicly, would turn other European countries against Britain and make an